JPH0543315Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a hydraulic continuously variable transmission, and particularly to one that transmits input torque by dividing it into hydraulic system torque and mechanical system torque.

(Conventional technology) Conventionally, as this type of hydraulic continuously variable transmission,
A set of variable displacement pumps and
It is equipped with a motor unit, a differential gear mechanism that distributes the input torque into hydraulic torque and mechanical torque generated by the pump and motor unit, and a low clutch and a high clutch for changing the torque distribution by the differential gear mechanism. and high range to switch the connection and disconnection of the low clutch and high clutch, and the above 1.
It is known that speeds can be changed continuously and steplessly by changing the amount of pressure oil discharged from a pump and motor unit.

Here, the relationship between the pressure oil discharge amount and the gear ratio in the pair of pump and motor units is shown in FIG. In this figure, in the low range and low gear ratio region, the discharge amount A ₁ of the motor side unit is set to the maximum value.
The gear ratio is raised by gradually increasing the discharge amount B ₁ of the pump side unit while keeping it constant at Dmax, and conversely, in the low range high gear ratio region, the discharge amount B ₂ of the pump side unit is kept constant at the maximum value Dmax. The gear ratio is increased by gradually decreasing the discharge amount _A2 of the motor side unit while maintaining the same. moreover,
In the low gear ratio region of the high range, the gear ratio is raised by gradually increasing the discharge volume A ₃ of the pump side unit while the discharge volume B ₃ of the motor side unit is held constant at the maximum value Dmax, and the transmission ratio is increased in the high range. Conversely, in the region, the gear ratio is increased by gradually decreasing the discharge amount _{B4 of the motor side unit while keeping the discharge amount A4 of} the pump side unit constant at the maximum value Dmax.

(Problem that the invention attempts to solve) By the way, in such a hydraulic continuously variable transmission,
When switching between low range and high range, normally, priority is given to switching the high clutch on and off, and
At the same time, the low clutch is also switched on and off, but due to hydraulic control, there is a time delay in switching on and off both clutches, and this poses a problem in that smooth switching is not possible. .

In addition, in a hydraulic continuously variable transmission, leakage occurs due to the influence of oil temperature, which changes the volumetric efficiency of the pump and motor unit. If the amount has decreased due to leakage, it is necessary to reduce the discharge amount _A2 of the motor side unit as shown by the imaginary line _C2 in FIG. 9 in order to obtain the target gear ratio. However, if you switch from the low range to the high range in this state, when the motor side unit changes to the pump, the discharge amount of the unit will be the theoretical predetermined discharge amount without any change in volume at the time of switching.
Since it is less than D ₁ , the discharge amount of the motor side unit in the high range decreases relatively, and the gear ratio suddenly and significantly changes (Δe).
It will shift to the low side and the switching will not be performed smoothly.
At this time, since the output side rotation speed (vehicle speed) is constant, the rotation speed of the rotating shaft of the unit that changes from the motor to the pump increases rapidly. In other words, since the discharge amount of the pump side unit is lower than the theoretical value (D ₁ ) with respect to the discharge amount of the motor side unit in the high range, the load that the pump side unit receives from the motor side unit becomes relatively small. In order to compensate for this decrease in the discharge amount, the rotational speed of the pump side unit increases rapidly. In addition, even if the discharge amount of the pump side unit and the hydraulic oil amount of the motor side unit decrease due to leakage when switching from the high range to the low range, the discharge amount _A3 of the pump side unit must be increased to obtain the target gear ratio. Then, when the pump-side unit switches to the motor, the gear ratio shifts to the low side, but since the gear ratio is shifted to the downshift side, there is usually little effect in relation to sudden gear changes such as kickdown, and the changeover is smooth. There are few requests for change.

The present invention has been devised in view of these points, and its purpose is to ensure braking in the low range while making it possible to switch between the low range and the high range by simply switching on and off the high clutch. At the same time, by preventing the rotational speed of the rotating shaft of the unit that changes from the motor to the pump from increasing rapidly when switching from the low range to the high range, sudden changes in the gear ratio are prevented, thereby making the switching smoother. There is a particular thing.

(Means for Solving the Problem) In order to achieve the above object, the solution of the present invention is a hydraulic continuously variable transmission that uses a variable displacement pump and motor unit, and input torque to the pump. & a differential gear mechanism that distributes hydraulic torque and mechanical torque from the motor unit, and a low clutch and a high clutch for changing the torque distribution by the differential gear mechanism, and when in the low range, the low clutch is connected and the On the other hand, when the high range is selected, the high clutch is disconnected, and when the high range is selected, the reverse connection and disconnection state is established.As a result of switching between the low range and the high range, one unit of the pair of pump and motor units is switched from the pump to the motor, and the other unit is switched from the pump to the motor. It is assumed that the motor is switched to the pump and that both the high clutch and the low clutch are disconnected when in reverse mode.

In such a hydraulic continuously variable transmission, the torque transmission system of the low clutch is provided with a one-way clutch in series with the low clutch that cuts off torque transmission in the opposite direction to the torque transmission direction in the low range. A coasting clutch that enables directional torque transmission is provided in parallel with the one-way clutch and low clutch.

(Function) With the above configuration, even in the present invention, when switching between the low range and the high range, the one-way clutch provided in the torque transmission system of the low clutch can be used without the need to switch the low clutch on and off at the same time as the high clutch is switched on and off. A state in which the low clutch is switched on and off at the same time as the high clutch is switched on and off will automatically occur.
That is, when switching from the low range to the high range, the one-way clutch cuts off torque transmission in the high range, which is the opposite direction to the low range torque transmission direction in the low clutch torque transmission system, so it is as if the low clutch is disconnected. . On the other hand, when switching from the high range to the low range, the one-way clutch does not cut off torque transmission in the torque transmission system of the low clutch, and the low clutch remains connected.

Also, if you reduce the discharge amount of the motor side unit in order to obtain the target gear ratio without being affected by leakage when in the low range, when switching from the low range to the high range in this state,
There is a risk that the rotational speed of the rotating shaft of the unit that changes from the motor to the pump will suddenly increase and the gear ratio will change rapidly, but in the case of the present invention, at the time of this switching, the low clutch is still in the connected state, and the low clutch and one-way clutch are Since the torque transmission system, including the I can do it.

Furthermore, during engine braking in which the torque transmission system of the low clutch requires torque transmission in the opposite direction to the normal torque transmission direction in the low range, a coasting clutch provided in parallel with the one-way clutch is connected to the torque transmission system of the low clutch. Since torque transmission in the opposite direction becomes possible, engine braking can be performed reliably.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with

1 to 4 show a hydraulic continuously variable transmission according to an embodiment of the present invention. In FIG. 1, 1 is a casing, 2 is a primary shaft rotatably disposed within the casing 1, and one end of the primary shaft 2 is drivingly connected to an output shaft 40 of the engine via a clutch 3. ing. Reference numerals 4 and 5 designate a set of variable displacement type first and second pump and motor units (hereinafter referred to as first and second units), and the rotation shafts 4a and 5a of both units 4 and 5 are connected to the primary pump and motor units, respectively. Shaft 2
is placed parallel to.

The primary shaft 2 is provided with a planetary differential gear mechanism 6 for distributing input torque from the engine output shaft 40 into hydraulic torque and mechanical torque generated by the first and second units 4 and 5. The planetary differential gear mechanism 6 includes a sun gear 7 rotatably supported by the primary shaft 2.
a pair of planetary gears 9, 9 meshing with the sun gear 7 and fixedly supported by the primary shaft 2 via the carrier 8;
9 and a ring gear 10 that meshes with the ring gear 9. A first transmission gear 11 is integrally provided to the sun gear 7, and the first transmission gear 11 is connected to the first unit 4.
It meshes with the second transmission gear 12 fitted onto the rotating shaft 4a. Further, the ring gear 10 is connected to a third transmission gear 13 rotatably supported by the primary shaft 2.
3 meshes with a fourth transmission gear 14 fixedly supported by the rotating shaft 5a of the second unit 5.

Further, a fifth transmission gear 15 is rotatably supported on the rotation shaft 4a of the first unit 4, and the fifth transmission gear 15 is connected to the rotation shaft 4a of the first unit 4 via a low clutch 16. At the same time, it meshes with the sixth transmission gear 17 rotatably supported by the primary shaft 2. The sixth transmission gear 17 is connected to the third transmission gear 13 or the ring gear 10 of the planetary differential gear mechanism 6 via a high clutch 18. Both the low clutch 16 and the high clutch 18 are hydraulic clutches, and the low clutch 16 is mounted on the rotating shaft 4a of the first unit 4, and the high clutch 1
8 are respectively positioned on the primary shaft 2 and arranged in a biaxial state.

As shown in FIGS. 2 and 3, the sixth transmission gear 17 is a final reduction gear 19.
A final pinion gear 20 is coaxially formed integrally with the reduction gear 19, and both gears 19 and 20 are rotatably supported by the casing 1. The final pinion gear 20 is a final ring gear 22 fixed to the case 21a of the differential device 21.
The drive torque transmitted to the final ring gear 22 is configured to be transmitted from the differential device 21 to the left and right wheels (not shown) via the drive shafts 23, 23.

Furthermore, in FIG. 4, 24 is the casing 1
A reverse shaft is rotatably arranged in parallel with the primary shaft 2, and the reverse shaft 24 has a seventh transmission gear 25 that meshes with the first transmission gear 11 on the primary shaft 2.
is formed integrally with the reverse shaft 24, and a reverse gear 26 is rotatably supported. The reverse gear 26 is connected to the reverse shaft 24 via a reverse clutch 27, and meshes with the sixth transmission gear 17 on the primary shaft 2 via a reverse idle gear 28 (see FIG. 2). ).

As a feature of the present invention, in the torque transmission system of the low clutch 16, there is a fifth transmission gear between the rotation shaft 4a of the first unit 4 and the fifth transmission gear 15.
A one-way clutch 29 that interrupts torque transmission from the transmission gear 15 to the rotating shaft 4a of the first unit 4 (torque transmission in the opposite direction to the torque transmission direction in the low range) is disposed in series with the low clutch 16. A coasting clutch 30 is disposed in parallel with the one-way clutch 29 and the low clutch 16. The coasting clutch 30 is a hydraulic clutch, and connects the fifth transmission gear 15 to the rotating shaft 4a of the first unit 4 to enable torque transmission from the fifth transmission gear 15 to the rotating shaft 4a of the first unit 4, regardless of the one-way clutch 29 during engine braking. It is. Note that 31 is an overdrive brake disposed around the outer periphery of the low clutch 16.

Next, the operation of the hydraulic continuously variable transmission will be explained with reference to FIGS. 5 to 9.

FIG. 5 shows the torque transmission path in the case of the low range. In the case of the low range, only the low clutch 16 of the low clutch 16, high clutch 18 and reverse clutch 27 is connected, and the other clutches 18 and 27 are disconnected. The input torque from the engine output shaft is transmitted to the planetary gear 9 side of the planetary differential gear mechanism 6 via the primary shaft 2, and the hydraulic system torque (corresponding to the thick broken line in the figure) is transmitted by the planetary differential gear mechanism 6. and mechanical torque (corresponding to the thin broken line in the figure). Hydraulic system torque is transmitted from the ring gear 10 of the planetary differential gear mechanism 6 to the third and fourth gears.
It is transmitted to the rotating shaft 5a of the second unit 5 via the transmission gears 13 and 14, so that the second unit 5 operates as a pump, and the first unit 4
It receives pressure oil discharged from the second unit 5 and operates as a motor. On the other hand, the mechanical torque is transmitted from the sun gear 7 of the planetary differential gear mechanism 6 to the first and second
The torque is transmitted via the transmission gears 11 and 12 to the rotating shaft 4a of the first unit 4, which operates the motor as described above, and merges with the hydraulic system torque. This combined driving torque is transmitted from the low clutch 16 to the final reduction gear 19 (wheel side) via the fifth and sixth transmission gears 15 and 17.

Further, FIG. 6 shows the torque transmission path in the case of high range. In this high range, only the high clutch 18 is connected, and the low clutch 16 and reverse clutch 27 are disconnected. The input torque is divided into hydraulic system torque and mechanical system torque by the planetary differential gear mechanism 6, as in the case of the low range described above. Hydraulic system torque is transmitted from the sun gear 7 of the planetary differential gear mechanism 6 to the first transmission gear via the first and second transmission gears 11 and 12.
The pressure is transmitted to the rotating shaft 4a of the unit 4, whereby the first unit 4 operates as a pump, and the second unit 5 receives the pressure oil discharged from the first unit 4 and operates as a motor. On the other hand, the mechanical torque is determined by the ring gear 1 of the planetary differential gear mechanism 6.
0 to the third transmission gear 13, and merges with the hydraulic system torque transmitted from the rotating shaft 5a of the second unit 5, which operates the motor as described above, to the third transmission gear 13 via the fourth transmission gear 14. . The combined driving torque is transmitted from the high clutch 18 to the final reduction gear 1 via the sixth transmission gear 17.
9.

Furthermore, FIG. 7 shows the torque transmission path in the case of reverse. In this reverse case, low clutch 16 and high clutch 1
8 are both disconnected, and only the reverse clutch 27 is connected. The input torque is divided into hydraulic system torque and mechanical system torque by the planetary differential gear mechanism 6, and the hydraulic radial torque is transmitted to the ring gear 10 of the planetary differential gear mechanism 6 as in the case of the low range.
is transmitted to the rotating shaft 5a of the second unit 5 via the third and fourth transmission gears 13 and 14, so that the second unit 5 operates as a pump and the first unit 4 operates as a motor. On the other hand, the mechanical torque is transmitted from the sun gear 7 of the planetary differential gear mechanism 6 to the first transmission gear 11.
After joining with the hydraulic torque transmitted from the rotating shaft 4a of the first unit 4 to the second transmission gear 12, the torque is transmitted to the reverse shaft 24 via the seventh transmission gear 25. The driving torque transmitted to the reverse shaft 24 is transmitted from the reverse clutch 27 to the final reduction gear 19 via the reverse gear 26, the reverse idle gear 28, and the sixth transmission gear 17.
In the case of this reverse, a very large drive torque is not required, so the hydraulic system torque may be eliminated by the second unit and only the mechanical system torque may be transmitted to the wheels as the drive torque.

In the case of the above-mentioned low range and high range, the hydraulic discharge amount of the pump-side unit 5 or 4 that operates the pump is adjusted so that the distance between the pump-side unit 5 or 4 and the motor-side unit 4 or 5 that operates the motor is adjusted. To change the distribution of hydraulic system torque and mechanical system torque in the planetary differential gear mechanism 6 by making the transmission rate of the hydraulic system torque variable in the planetary differential gear mechanism 6 and by switching the low clutch 16 and the high clutch 18 into and out, that is, by switching between the low range and the high range. This allows gear changes to be performed continuously and steplessly.

Here, the relationship between the rotational speed and the gear ratio (output rotation/input rotation) of the first unit 4 and the fifth, sixth, and third transmission gears 15, 17, and 13 is shown in FIG. The rotational speed characteristic D of the third transmission gear 13 is maximum when the gear ratio is zero, and decreases linearly as the gear ratio increases. The rotational speed characteristic C of the sixth transmission gear 17 increases linearly from zero as the gear ratio increases. Then, when the speed ratio em is such that the rotational speed characteristic D of the third transmission gear 13 and the rotational speed characteristic C of the sixth transmission gear 17 intersect, switching between the low range and the high range is performed. In addition, the rotational speed characteristic A of the first unit 4 increases linearly from zero in the low range as the gear ratio increases, while in the high range it decreases linearly from the rotational speed at the gear ratio em, and reaches the maximum gear ratio. It becomes zero when the ratio is The rotational speed characteristic B of the fifth transmission gear 15 increases linearly as the gear ratio increases, and coincides with the rotational speed characteristic A of the first unit 4 in the low range.

Further, the relationship between the amount of pressure oil discharged from the first and second units 4 and 5 and the gear ratio is shown in FIG. In this figure, the discharge amount characteristics A ₁ to _{A 4} of the first unit 4 are shown by broken lines, and the discharge amount characteristics B ₁ to B ₄ of the second unit 5 are shown by solid lines, respectively. In other words, in the low gear ratio region of the low range, the discharge amount A ₁ of the first unit 4, which operates the motor, is held constant at the maximum value Dmax, while the discharge amount B ₁ of the second unit 5, which operates the pump, increases.
The gear ratio is raised by gradually increasing
The transmission ratio is increased by gradually decreasing the discharge amount A ₂ of the first unit 4 while the discharge amount B ₂ of the first unit 4 is held constant at the maximum value Dmax. Furthermore, in the low gear ratio region of the high range, the discharge volume A 3 of the first unit 4 that operates the pump is gradually increased while the discharge volume B ₃ of the second unit ₅ that operates the motor is held constant at the maximum value Dmax. This increases the gear ratio,
Conversely, in the high gear ratio region of the high range, the gear ratio is increased by gradually decreasing the discharge amount B 4 of the second unit 5 while keeping the discharge amount A ₄ of the first unit ₄ constant at the maximum value Dmax. .

By the way, when switching between a low range and a high range, in a conventional hydraulic continuously variable transmission, the low clutch 16 is switched on and off and the high clutch 18 is switched so that only the low clutch 16 is connected in the low range and only the high clutch 18 is connected in the high range.
It was necessary to simultaneously switch on and off.

On the other hand, in the hydraulic continuously variable transmission of the embodiment described above, the torque transmission system of the low clutch 16 is provided between the rotating shaft 4a of the first unit 4 and the fifth transmission gear 15. Since a one-way clutch 29 is provided to cut off torque transmission to the rotating shaft 4a of the first unit 4, even if the low clutch 16 is connected in the high range in the same way as in the low range, the one-way clutch 29 will cause the low range to operate as if it were in the high range. When the low clutch 16 is disconnected, a state can be automatically created in which the low clutch 16 is switched on and off at the same time as the high clutch 16 is switched on and off when switching between the low range and the high range. That is, in the torque transmission system of the low clutch 16, in the low range, the driving torque is transmitted from the rotating shaft 4a of the first unit 4 to the fifth transmission gear 15 via the low clutch 16 and the one-way clutch 29, regardless of the installation of the one-way clutch 29. The connected state of the lock clutch 16 is ensured. On the other hand, as shown in FIG. 8, the rotational speed of the fifth transmission gear 15 (characteristic B)
In the high range where the rotational speed is higher than the rotational speed of the first unit 4 (characteristic A), the one-way clutch 29
is idling, and the transmission from the fifth transmission gear 15 to the first unit 4
The torque transmission to the rotating shaft 4a, that is, the torque transmission in the opposite direction to the torque transmission in the low range is cut off, and the torque transmission system of the low clutch 16 becomes the same as the state in which the low clutch 16 itself is disconnected.

Therefore, in this way, when switching between the low range and the high range, it is only necessary to switch the high clutch 18 on and off, and there is no need to switch the low clutch 16 on and off at the same time.
Switching can be carried out smoothly, and no shocks will occur due to timing differences in switching between the two clutches.

In addition, in order to obtain the target gear ratio without being affected by leakage in the low range, the discharge amount of the first unit 4 that operates the motor is reduced, that is, its discharge amount characteristics are changed from A ₂ to C ₂ . In this case, if the low range is switched to the high range in this state, there is a risk that the gear ratio e will change rapidly and significantly (Δe), and the rotational speed of the rotating shaft 4a of the first unit 4 will suddenly increase. However, in the case of this embodiment, at the time of this switching, the low clutch 16 is still in the connected state as described above, and the torque transmission system from the low clutch 16 to the transmission gear 15 through the one-way clutch 29 is in a state where driving resistance is applied on the output side. This torque transmission system prevents the rotational speed of the rotating shaft 4a of the first unit 4 from increasing rapidly. As a result, rapid changes in the gear ratio can be prevented, and switching can be made more smoothly.

Furthermore, even in the case of low range, engine braking requires torque transmission from the fifth transmission gear 15 to the rotating shaft 4a of the first unit 4 in the torque transmission system of the low clutch 16, that is, torque transmission from the wheel side to the engine side. Sometimes, by connecting the coasting clutch 30 provided in parallel with the one-way clutch 29 to the torque transmission system of the low clutch 16, torque can be transmitted from the wheel side to the engine side regardless of the installation of the one-way clutch 29. It is possible to perform engine braking reliably.

Furthermore, in the above embodiment, in particular, a one-way clutch 29 is provided in series with the low clutch 16 between the rotating shaft 4a of the first unit 4 and the fifth transmission gear 15 in the torque transmission system of the low clutch 16. Since the coasting clutch 30 is provided in parallel with the one-way clutch 29 and the low clutch 16, the space required for arranging these three clutches 16, 29, 30 can be minimized, and the transmission It can contribute to miniaturization.

Note that the present invention is not limited to the above-mentioned embodiments, but includes various other modifications. For example, in the above embodiment, the present invention is applied to a case where a planetary gear mechanism is used as a differential gear mechanism that divides input torque into hydraulic system torque and mechanical system torque, but various other differential gear mechanisms can also be used. Of course, it can be similarly applied to the case where . Further, the low clutch 16 and high clutch 18 for changing the torque distribution by the differential gear mechanism are not limited to those arranged in a biaxial state as in the above embodiment, but can also be applied to those arranged in a coaxial state. can.

(Effects of the invention) As described above, according to the hydraulic continuously variable transmission of the invention, the one-way clutch provided in the torque transmission system of the low clutch can be used without the need to switch the low clutch on and off at the same time as the high clutch is switched on and off. This makes it possible to realize a state in which the low clutch is switched on and off at the same time as the high clutch is switched on and off, and the rotational speed of the rotating shaft of the unit that changes from the motor to the pump increases rapidly when switching from the low range to the high range. This makes it possible to prevent sudden changes in the gear ratio, thereby making it possible to significantly smoothen the switching between the low range and the high range. Furthermore, regardless of the installation of the one-way clutch, engine braking can be ensured in the low range, so this has excellent practical effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a sectional view of a hydraulic continuously variable transmission; FIG. 2 is a diagram showing the meshing states of various gears as seen along the - line in FIG. 1; Figures 3 and 4 are - of Figure 2, respectively.
FIG. Fifth
The figure is a schematic diagram showing the torque transmission path in the case of low range, Figure 6 is a diagram equivalent to Figure 5 in the case of high range, Figure 7 is a diagram equivalent to Figure 5 in the case of reverse, and Figure 8 is a diagram equivalent to Figure 5 in the case of reverse. FIG. 9 is a diagram showing the rotational speed characteristics of the first unit, etc., and FIG. 9 is a diagram showing the discharge amount characteristics of the first and second units. 4...First unit, 5...Second unit, 6
...Planetary differential gear mechanism, 16...Low clutch,
18...High clutch, 29...One-way clutch, 30...Coasting clutch.

Claims (1)

[Scope of utility model registration request] A variable displacement pump and motor unit, a differential gear mechanism that distributes input torque into hydraulic torque and mechanical torque from the pump and motor unit, and a differential gear mechanism for changing the torque distribution by the differential gear mechanism. a low clutch and a high clutch, and when in the low range, the low clutch is connected and the high clutch is disconnected, and on the other hand,
When in the high range, the connection and disconnection state is reversed, and when switching between the low range and the high range, the above
Of the pump and motor units in the set, one unit operates from the pump to the motor, and the other unit from the motor to the pump, and when in reverse, there is a hydraulic system that disconnects both the high and low clutches. In the gear transmission, the torque transmission system of the low clutch is provided with a one-way clutch in series with the low clutch that cuts off torque transmission in the opposite direction to the torque transmission direction in the low range, and also transmits torque in the opposite direction during engine braking. A hydraulic continuously variable transmission characterized in that a coasting clutch that enables transmission is provided in parallel with the one-way clutch and the low clutch.